The prior art sharpening devices for crayons and similar marking instruments typically included a conical housing with two flat, angled walls provided with symmetrical sharpening elements extending from the base of the housing substantially to its apex. These sharpening elements usually comprised rectangular openings sized so that the edges of the openings engaged and shaved the surface of a crayon pressed into the openings.
To sharpen a crayon in the prior art devices, one inserted the crayon into the sharpener and rotated the crayon while simultaneously pressing the crayon into the sharpening openings. As the crayon rotated, the edges of the sharpening openings removed a thin layer of wax, plastic or similar material from the surface of the crayon, giving the crayon a smooth, pointed, conical shape suitable for marking or coloring. The shavings would then pass through the sharpening openings into an optional collection receptacle. An example of such a sharpener is illustrated in FIG. 12 herein.
Crayons and similar marking instruments are sold in a wide variety of sizes. For example, the CRAYOLA brand round wax crayons sold by Binney & Smith Inc. range from 0.360 inches to 0.570 inches in diameter. The prior art sharpeners, however, were not designed to sharpen all crayon sizes within such a range. On the contrary, the prior art sharpeners were usually limited to a predetermined crayon size. They could not accommodate crayons with a larger diameter and did not satisfactorily sharpen crayons with a smaller diameter.
In particular, sharpeners designed for relatively large crayons often lacked sufficient means for ensuring that small crayons were held in the proper sharpening position. Thus, it was frequently difficult to sharpen small crayons to the proper dimensions without breaking or cracking their tips during the sharpening process. Simply expanding the dimensions of sharpeners intended for small diameter crayons to accommodate larger diameter crayons was also unsuccessful as these devices lacked the structural strength to resist the forces and stresses generated while sharpening large crayons.
As a result, a number of separate and individual sharpening devices tailored for each crayon size, or a series of such sharpening devices mounted in a single unit, were required to sharpen the range of commercially available crayons. This was both inconvenient and impractical, particularly for young children (frequently heavy crayon users) who were required to identify and keep track of the particular sharpener which matched each of the presently available crayon sizes.
The present invention provides a single, universal crayon sharpener which, unlike those of the prior art, will sharpen from relatively large diameter crayons (e.g. 0.570 inches in diameter) to relatively small diameter crayons (e.g. 0.360 inches in diameter). The sharpener of the invention employs asymmetrical sharpening means and internal guide means to ensure that crayons of many different sizes may be efficiently and properly sharpened to the correct dimensions, thus eliminating the need for multiple sharpeners of different sizes.
The invention, in addition, provides a universal sharpener that may be reinforced to withstand the pressures and forces generated during the sharpening of relatively large crayons or other difficult to sharpen marking instruments. Furthermore, the invention provides a sharpener that is cost efficient and simple to manufacture.